| Year | Value (SE) |
|---|---|
| 2000 | 0.4423 (0.1984) |
| 2001 | 0.4107 (0.0348) |
| 2002 | 0.7513 (0.0723) |
| 2003 | 0.7105 (0.0845) |
| 2004 | 0.5914 (0.1176) |
| 2005 | 0.5874 (0.1077) |
| 2006 | 0.6389 (0.0859) |
| 2007 | 0.8268 (0.0714) |
| 2008 | 1.0049 (0.1655) |
| 2009 | 0.7034 (0.1073) |
| 2010 | 0.9356 (0.1866) |
| 2011 | 0.7928 (0.1779) |
| 2012 | 0.8018 (0.0940) |
| 2013 | 1.1326 (0.2525) |
| 2014 | 0.8569 (0.1436) |
| 2015 | 0.4970 (0.1413) |
| 2016 | 0.4804 (0.0553) |
| 2019 | 0.6950 (0.1284) |
| 2020 | 0.6739 (0.1706) |
| 2021 | 0.5303 (0.5894) |
| 2022 | 0.5636 (0.1795) |
| 2023 | 0.5756 (0.1195) |
